Introduction: The “Physical Limits” of Traditional Heat Pumps
In regions with extreme cold—such as Northern Europe, North America, or Central Asia—the reliability of air-source heat pumps often hinges on performance during the coldest days of winter. When outdoor temperatures drop below -15°C, traditional single-stage compression heat pumps typically hit two physical limits: first, a significant drop in heating capacity, preventing the system from maintaining the set temperature; and second, an excessively high compression ratio that drives discharge temperatures toward safety limits, causing frequent protective shutdowns or forcing reliance on energy-intensive electric auxiliary heating.
To overcome this industry-recognized bottleneck, Fowrise has deeply integrated EVI technology into its DC inverter series, effectively breaking through the limitations imposed by extreme cold.
Technical Logic: Advancing from Single-Stage Compression to a Quasi-Two-Stage Cycle
EVI is not merely an adjustment of parameters; it fundamentally alters the refrigerant compression process.
In traditional heat pumps, the refrigerant undergoes only a single stage of compression. In contrast, the Fowrise EVI system incorporates an intermediate-pressure vapor injection circuit. When the system detects extreme cold conditions, a portion of intermediate-pressure gaseous refrigerant is precisely injected into the compressor’s “vapor injection port.”
This physically achieves “quasi-two-stage compression”: the refrigerant is first compressed to an intermediate pressure, mixed with the injected gas (which lowers its temperature), and then undergoes a second stage of high-pressure compression. This design not only increases the refrigerant mass flow rate but also effectively lowers the compressor’s discharge temperature.
Breaking Limits: The Engineering Performance of Fowrise EVI
- Overcoming Heating Capacity Degradation: Thanks to the enthalpy-enhancing effect of intermediate-pressure vapor injection, the unit effectively compensates for heating capacity loss in extreme cold. Compared to traditional single-stage compression heat pumps of the same capacity, Fowrise EVI units deliver significantly higher heating output in temperatures ranging from -20°C to -30°C, meeting the building’s base heating load without the need for energy-intensive electric auxiliary heating.
- Overcoming Temperature Limits of Core Components: The high compression ratios caused by extreme cold often lead to skyrocketing discharge temperatures in standard compressors. The intermediate vapor injection (EVI) process in Fowrise EVI units acts as a form of “active cooling” for the compressor, effectively keeping discharge temperatures well below critical safety limits. This fundamentally prevents the carbonization of refrigeration oil caused by high temperatures, significantly reduces mechanical wear, and ensures the compressor’s long-term, stable operation.
- Pushing the boundaries of defrosting and energy efficiency: By combining EVI technology with our optimized system control logic, we effectively reduce the frequency of evaporator frosting in low-temperature, high-humidity environments. Longer intervals between defrost cycles mean the unit maintains effective heating for extended periods; this not only boosts the overall Coefficient of Performance (COP) in extreme cold but also prevents indoor temperature fluctuations caused by frequent defrosting.
Built for reliability, proven under extreme conditions
Heat pumps are systems that rely heavily on manufacturing consistency. To ensure that every Fowrise EVI unit delivered to a customer meets design expectations, we implement rigorous quality control procedures before the product leaves the factory.
Every unit undergoes continuous operation testing at the factory under simulated extreme cold conditions to verify its heating performance, discharge temperature, and defrost logic. Only units that fully meet all design specifications are approved for packaging and shipment.
Amidst climate change and the global energy transition, the market for extreme-cold heat pumps is experiencing explosive growth. The Fowrise EVI series is the ideal tool for you to capture a share of this high-profit market.
